1. Field of the invention
This invention relates to a machine head for guitars, used for adjusting the tension of guitar strings, and, more particularly, to a machine head designed to easily hold a string to the head of a guitar.
2. Description of the prior art
In general, a machine head for guitars, mounted to the head of a guitar, is used for holding the end of a string to the head of the guitar while appropriately tensioning the string by rotating an adjusting knob. FIGS. 8 and 9 show a conventional machine head for guitars.
As shown in the drawings, the body 430 of a conventional machine head 400 has two bores, a vertical sleeve bore 432 and a horizontal bore 434 communicating with each other. The vertical sleeve bore 432 receives a rotatable winding peg 410. The peg 410 is used for adjusting the tension of a string by winding or unwinding the string thereon or therefrom. On the other hand, the horizontal bore 434 receives a worm shaft 450 used for rotating the winding peg 410.
In a detailed description, the stepped worm shaft 450 has a worm 451 at its large-diameter outside end portion. A connection shaft portion 452, having an internal thread 453, is formed at the small-diameter inside end portion of the worm shaft 450. Therefore, when the worm shaft 450 is inserted into the horizontal bore 434 of the body 430, the worm 451 is placed within the horizontal bore 434, while the connection shaft portion 452 protrudes outwardly from a tapered horizontal sleeve 433 of the body 430 to a length.
After two washers 481 and 482 are fitted over the worm shaft 450 at a position externally protruding from the body 430, a first set screw 491 is driven into the internal thread 453 of the worm shaft 450. In such a case, the screw 491 passes through a connection bore 441 of the adjusting knob 440. The above adjusting knob 440 and the worm shaft 450 are thus integrated together while being rotatably assembled with the body 430.
A vertical sleeve 431 projects upwardly from the top of the body 430 and has the sleeve bore 432 therein, with an internal thread 431a formed on the interior surface of the sleeve bore 432. An annular stopper 431b is formed at the inside end of the internal thread 431a as shown in the FIG. 9, with a worm wheel 460 placed in the seat formed within the body 430 at a position under the stopper 431b and engaging with the worm 451 of the worm shaft 450.
In addition, a serration 461 is formed on the interior surface of the center hole of said worm wheel 460, while a serrated portion 411 is formed at the stepped lower end of the winding peg 410 and engages with the serration 461 of the worm wheel 460. An internal thread 412 is formed on the lower end portion of the winding peg 410, thus allowing a second set screw 492 to be threaded into the winding peg 410 so as to assemble the worm wheel 460 with the winding peg 410.
Accordingly, when the winding peg 410 is inserted into the vertical sleeve bore 432 of the body 430, the lower serrated portion 411 of the peg 410 is fitted into the serration 461 of the worm wheel 460 prior to threading the screw 492 into the internal thread 412 of the winding peg 410. The winding peg 410 and the worm wheel 460 are thus brought into engagement with each other while being rotatably held in the body 430 by the annular stopper 431b. The lower opening of the vertical sleeve bore 432 is closed by a cover 470, thus hiding the worm wheel 470 from the outside.
The body 430 is set in a locking hole of the guitar head at the vertical sleeve 431. In such a case, a locking member 420, having an external thread 421 corresponding to the internal thread 431a of the vertical sleeve 431, is locked to the vertical sleeve 431 along with a washer 483, thus locking the machine head 400 to the head of the guitar. In such a case, the winding peg 410 is inserted into the body 430 through the central bore 422 of the locking member 420.
When it is necessary to hold a string to the machine head 400, one end of the string is inserted into a string hole 413 formed at a spool portion of the winding peg 410 prior to rotating the adjusting knob 440 while catching the string around the string hole 413 with the fingers. When the adjusting knob 440 is rotated as described above, the worm shaft 450 is rotated, and so the worm wheel 460, engaging with the worm 451 of the shaft 450, is rotated. The winding peg 410 is thus rotated. When the peg 410 is rotated, the string is appropriately wound around the spool portion of the peg 410 several turns until the end of the string is frictionally held by the tensioned turns of the string and is prevented from being unexpectedly removed from the peg 410 due to the tensile force of the string. The desired tension of the string is, thereafter, achieved by further and precisely rotating the adjusting knob 440 in either direction.
However, the conventional machine head is problematic in that it is necessary for a user to catch the end of the string at a position around the spool portion of the winding peg with the fingers until the string is firmly and frictionally held on the winding peg due to a rotating action of the adjusting knob. This is inconvenient to the user while holding the string on a guitar.